The printing industry, in general, finds many applications for the use of water-based inks and overprint varnishes as a means of meeting increasingly stringent solvent effluent regulations. Present-day water-based inks often fail to satisfy these regulations as well as the necessary printability, stability, and performance properties required for commercial inks. For example, the various ethylene-acrylic acid copolymer salts of U.S. Pat. No. 3,607,813, the disclosure of which is incorporated herein by reference (for the printing process descriptions therein), in addition to requiring complex polymer and ink preparations, lack in performance on certain substrates. Other such aqueous or semi-aqueous systems proposed for printing inks contain polymers such as styrene-butadiene or polyacrylate latex systems but these systems also have serious drawbacks including being nondispersible in their aqueous media after short drying periods which complicates equipment clean up. Other water soluble or dispersible polymers suggested for printing ink use are disclosed in U.S. Pat. No. 4,072,644.
The present invention provides substantial improvements in the preparation, stability, and performance of water-based inks for printing and coating, particularly in regard to flow-out, smoothness, uniformity and optical density on a great variety of substrates.